Fluoxetine and Olanzapine interaction
Fluoxetine and Olanzapine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Fluoxetine (Prozac) label · effective 2026-01-08
When using PROZAC and olanzapine in combination, also refer to Boxed Warning section of the package insert for Symbyax.
When using PROZAC and olanzapine in combination, also refer to Boxed Warning section of the package insert for Symbyax .
When using PROZAC and olanzapine in combination, also refer to the Contraindications section of the package insert for Symbyax.
Do not use thioridazine within 5 weeks of discontinuing PROZAC ( 4.2 , 5.11 , 7.7 , 7.8 ) When using PROZAC and olanzapine in combination, also refer to the Contraindications section of the package insert for Symbyax ( 4 )
When using PROZAC and olanzapine in combination, also refer to the Warnings and Precautions section of the package insert for Symbyax.
From the Olanzapine (Zyprexa) label · effective 2026-02-11
When using ZYPREXA and fluoxetine in combination, also refer to the Boxed Warning section of the package insert for Symbyax.
When using ZYPREXA and fluoxetine in combination, also refer to the Contraindications section of the package insert for Symbyax.
When using ZYPREXA and fluoxetine in combination, also refer to the Warnings and Precautions section of the package insert for Symbyax.
Use in Combination with Fluoxetine, Lithium, or Valproate When using ZYPREXA and fluoxetine in combination, the prescriber should also refer to the Warnings and Precautions section of the package insert for Symbyax.
Inhibitors of CYP2D6 Fluoxetine: Fluoxetine (60 mg single dose or 60 mg daily dose for 8 days) causes a small (mean 16%) increase in the maximum concentration of olanzapine and a small (mean 16%) decrease in olanzapine clearance.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.